The first major step in the cheese making process is the coagulation of the milk, such as by enzymatic hydrolysis of κ-casein. To achieve this end, enzyme extracts from calf stomachs, microbially produced enzymes, or other enzyme sources are utilized. The hydrolysis of κ-casein leads to destabilization of the colloidal system of the milk. This is followed by aggregation of the micelles into clusters. Over time, the clusters grow in size. This growth in size is followed by cross-linking between chains which eventually transform the milk into a gel or coagulum. Once a desired endpoint is reached in the coagulation process, the coagulum is “cut,” for example by traversing with wire knives to slice the coagulum into cubes. Accurate prediction of the optimal cutting time is an important factor in consistent, batch-to-batch quality and moisture content in the final cheese product.
The second major step in cheese making is syneresis, which initiates immediately following the coagulum cutting step. Syneresis is the phase separation process in cheese making that follows the cutting of the milk coagulum into cubes. Syneresis is generally promoted by thermal and/or mechanical treatments (cutting), and also may be slightly influenced by use of additives such as calcium chloride. During syneresis, rearrangement of the casein network, which constitutes the gel matrix, causes the shrinkage of the curd matrix and results in expulsion of whey from the curd grains, resulting in a solid:liquid mixture whose proportions change over time as syneresis endpoint nears.
Syneresis control influences cheese quality and yield as a result of its effects on moisture, mineral and lactose content of the curd. Syneresis also influences protein and fat losses in whey, which in turn affects cheese yield.
Curd syneresis is a kinetically complex process. Currently, there are no suitable techniques for reliably and reproducibly measuring syneresis as a means for studying and monitoring the syneresis process, particularly techniques adaptable to online, automated monitoring systems. The majority of techniques can be classed as either separation or dilution methods. Each method presents unique drawbacks.
At present, in the cheese industry worldwide, syneresis is empirically controlled by vat temperature, milk pH, stirring speed and time, depending on cheese type and the cheese maker's preferences. Unfortunately, inadequate curd moisture control resulting from such empirical process controls can lead to heterogeneous cheese ripening and quality, rather than providing homogenous conditions leading to a consistent end product from batch to batch. Better control of syneresis would give more consistent curd moisture content and pH, and more consistent curd concentration of minerals and lactose at the beginning of the curing process, resulting in a more homologous quality of product from batch to batch.
The present invention relates to a method of improving the quality of cheese produced from a curd and whey mixture. More specifically, the present method provides improved monitoring of both milk coagulation and curd syneresis during cheese making. Even more, the method and sensor are easily adapted for continuous, online monitoring of the cheese making process from initiation of coagulation to syneresis endpoint, and also prediction of endpoints for both processes, allowing better control of the entire cheese making process to ensure moisture content consistency and better cheese quality.